evolution/mail/mail-identify.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */

/*
 * Author :
 *  Dan Winship <danw@ximian.com>
 *
 *  Copyright 2000, Ximian, Inc. (www.ximian.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <string.h>

#include <glib.h>
#include <libgnomevfs/gnome-vfs-mime-utils.h>
#include "mail.h"

static const char *identify_by_magic (CamelDataWrapper *data, MailDisplay *md);

/**
 * mail_identify_mime_part:
 * @part: a CamelMimePart
 * @md: the MailDisplay @part is being shown in
 *
 * Try to identify the MIME type of the data in @part (which presumably
 * doesn't have a useful Content-Type).
 *
 * Return value: the MIME type, which the caller must free, or %NULL
 * if it could not be identified.
 **/
char *
mail_identify_mime_part (CamelMimePart *part, MailDisplay *md)
{
	const char *filename, *magic_type = NULL;
	CamelDataWrapper *data;
	char *name_type = NULL;

	filename = camel_mime_part_get_filename (part);
	if (filename) {
		/* GNOME-VFS will misidentify TNEF attachments as MPEG */
		if (!strcmp (filename, "winmail.dat"))
			return g_strdup ("application/vnd.ms-tnef");

#warning "does gnome_vfs_get_mime_type handle a plain filename as the 'text_uri'?"
		name_type = gnome_vfs_get_mime_type(filename);
	}

	data = camel_medium_get_content_object (CAMEL_MEDIUM (part));
	if (!camel_data_wrapper_is_offline (data))
		magic_type = identify_by_magic (data, md);

	if (magic_type && name_type) {
		/* If GNOME-VFS doesn't recognize the data by magic, but it
		 * contains English words, it will call it text/plain. If the
		 * filename-based check came up with something different, use
		 * that instead.
		 */
		if (!strcmp (magic_type, "text/plain"))
			return name_type;

		/* If if returns "application/octet-stream" try to
		 * do better with the filename check.
		 */
		if (!strcmp (magic_type, "application/octet-stream"))
			return name_type;
	}

	/* If the MIME part data was online, and the magic check
	 * returned something, use that, since it's more reliable.
	 */
	if (magic_type) {
		g_free(name_type);
		return g_strdup (magic_type);
	}

	/* Otherwise try guessing based on the filename */
	if (name_type)
		return name_type;

	/* Another possibility to try is the x-mac-type / x-mac-creator
	 * parameter to Content-Type used by some Mac email clients. That
	 * would require a Mac type to mime type conversion table.
	 */

#if 0
	/* If the data part is offline, then we didn't try magic
	 * before, so force it to be loaded so we can try again later.
	 * FIXME: In a perfect world, we would not load the content
	 * just to identify the MIME type.
	 */
	/* This is disabled as it just frustrates users more than it helps,
	   see discussion in bug #11778 */
	if (camel_data_wrapper_is_offline (data))
		mail_content_loaded (data, md, TRUE, NULL, NULL, NULL);
#endif

	return NULL;
}

static const char *
identify_by_magic (CamelDataWrapper *data, MailDisplay *md)
{
	CamelStreamMem *memstream;
	const char *type;

	memstream = (CamelStreamMem *)camel_stream_mem_new();
	if (camel_data_wrapper_write_to_stream (data, (CamelStream *)memstream) > 0)
		type = gnome_vfs_get_mime_type_for_data(memstream->buffer->data, memstream->buffer->len);
	else
		type = NULL;
	camel_object_unref(memstream);

	return type;
}